Experiment study of bed load particle velocity

Bed load transport rate can be calculated by using the particle velocity of transport sediment. However, few experiments have been conducted to directly measure bed sediment velocity. This paper presented a series of experiments conducted at an open channel flume to study bed load particle velocity at different stages of transport intensity. The flume is 13.5 m long and 0.6 m wide with a fixed bottom slope of 0.001. Four groups of uniformly sized sediments with mean sizes ranging from 0.45 mm to 4.75 mm are used. Flow discharge is measured at the end of flume using a rectangular weir ranging from 0.015 to 0.055 m3/s. The vertical distribution of flow velocity is measured using the Vectrino Velocity Profiler with a sampling frequency of 70 Hz. Bed load particle velocities are determined by particle tracking analysis of a series of images captured using a high-speed camera. The spatial and temporal averaged particle velocities and the statistical distribution of velocities are calculated and compared with empirical relations. Results showed that the spatial averaged particle velocity is much smaller than the saltation velocity of a single particle. A new linear relation for particle velocity is formulated based on the experimental data. Additionally, both measured particle velocities and transport directions nearly satisfy the normal distribution. Those experimental data for particle velocity provide opportunity to improve prediction of sediment transport.